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Documents printed by order of the General Assembly of North Carolina at its session of ...[1840;1841]

10
the beach, across which, in strong westerly winds, they have been
known sometimes to break into the ocean, satisfies me they were ful-ly
as stron^ as the currents from the sea, before the union of the wa-ters
of Albemarle witli those of Pamlico.
A conviction of these imaginary difficulties in the way of opening
Roanoke Inlet, has given origin to a project of an artificial harbour,
based upon the theory of there being a necessity of a conformity and
fixed proportion between the capacity of a harbour and its inlet; and
under such circumstances, that the influx and reflux of the tides are
adequate to free the harbour and preserve it from atteration. But it
is a well established theory that tidal currents do not contribute so
much to sand formations as has been supposed; and the effects which
liave been r.^cribed to them and to liiteral currents, are now readily
traced to the action of the leaves of the bottom*
It is true that some of the best harbours on our coast are mere arms
of the sea; but it is also true that harbours thus formed, are either ve-ry
good, or thpy are good for nothing. If the water is shoal, the bot-tom
will be affected by the waves of tJie bottom, and will soon fill
up. Sometimes the mouths will close, and cause the formation of
.salt ponds or lagunes. A harbour, therefore, under such circumstan-ces,
with no land water running into it, ought to be deep, its bottom
ought to be below the influence of the waves of the bottom, and its
entrance wide enough to admit a quantity of tide water to flow in and
out twice a day, sufiicient to keep the mud and other matter in agita-tion
and from settling. A tendency to form a bar at the inlet, and to
silting, can only be counteracted by contracting the entrance, and
thereby increasing the strength of the ebb tide; or by damming up
the waters at high tide; or by throwing in fresh water, to obtain an ar-tificial
scour. But, to widen an outlet, (which would be in accord-ance
with the above theory,) with the view of deepening it, is a plan
not yet tried, and is in direct opposition to the theory, or rather the
axiom, that the depth of streams is in the inverse ratio of their widths.
Surely this plan would not be practised in improving the entrance
into rivers, and certainly would not succeed in restoring an entrance
into a lagune. An artificial harbour, therefore, at Roanoke Inlet,
should be very deep. Agreeably to my estimate of the force of the
bottom leaves, on this part of the coast, it should be at least 20 feet
deep; and then it would be absolutely necessary to protect its en-trance
by stone walls, which, together with the excavation, and the
expense of a canal through Roanoke Island, and the walls between
the banks and the island, would swell the cost to many millions.
Du mouvcnient dcs nnda^ par. A. R. Emy.

10
the beach, across which, in strong westerly winds, they have been
known sometimes to break into the ocean, satisfies me they were ful-ly
as stron^ as the currents from the sea, before the union of the wa-ters
of Albemarle witli those of Pamlico.
A conviction of these imaginary difficulties in the way of opening
Roanoke Inlet, has given origin to a project of an artificial harbour,
based upon the theory of there being a necessity of a conformity and
fixed proportion between the capacity of a harbour and its inlet; and
under such circumstances, that the influx and reflux of the tides are
adequate to free the harbour and preserve it from atteration. But it
is a well established theory that tidal currents do not contribute so
much to sand formations as has been supposed; and the effects which
liave been r.^cribed to them and to liiteral currents, are now readily
traced to the action of the leaves of the bottom*
It is true that some of the best harbours on our coast are mere arms
of the sea; but it is also true that harbours thus formed, are either ve-ry
good, or thpy are good for nothing. If the water is shoal, the bot-tom
will be affected by the waves of tJie bottom, and will soon fill
up. Sometimes the mouths will close, and cause the formation of
.salt ponds or lagunes. A harbour, therefore, under such circumstan-ces,
with no land water running into it, ought to be deep, its bottom
ought to be below the influence of the waves of the bottom, and its
entrance wide enough to admit a quantity of tide water to flow in and
out twice a day, sufiicient to keep the mud and other matter in agita-tion
and from settling. A tendency to form a bar at the inlet, and to
silting, can only be counteracted by contracting the entrance, and
thereby increasing the strength of the ebb tide; or by damming up
the waters at high tide; or by throwing in fresh water, to obtain an ar-tificial
scour. But, to widen an outlet, (which would be in accord-ance
with the above theory,) with the view of deepening it, is a plan
not yet tried, and is in direct opposition to the theory, or rather the
axiom, that the depth of streams is in the inverse ratio of their widths.
Surely this plan would not be practised in improving the entrance
into rivers, and certainly would not succeed in restoring an entrance
into a lagune. An artificial harbour, therefore, at Roanoke Inlet,
should be very deep. Agreeably to my estimate of the force of the
bottom leaves, on this part of the coast, it should be at least 20 feet
deep; and then it would be absolutely necessary to protect its en-trance
by stone walls, which, together with the excavation, and the
expense of a canal through Roanoke Island, and the walls between
the banks and the island, would swell the cost to many millions.
Du mouvcnient dcs nnda^ par. A. R. Emy.